EDTA/纳米羟基磷灰石联合修复重金属污染土壤

土壤淋洗可能导致残留重金属活化，采用淋洗/钝化联合修复重金属污染土壤可在一定程度上减少这一影响。研究了EDTA淋洗、纳米羟基磷灰石钝化及两者联合修复对土壤重金属洗脱率、TCLP浸出浓度、化学形态分布的影响，构建了涵盖土壤重金属残留量、生物有效性和生理毒性的环境风险评价方法，对淋洗、钝化及其联合修复进行了评价。结果发现，EDTA淋洗对Pb和Cu的洗脱效果较好，对Zn浸出浓度的削减率较高。当EDTA投加量为2 g·L-1时，Zn的浸出浓度降低了70.40%。纳米羟基磷灰石对Pb和Zn具有较好的钝化效果，对Cu和Cd的钝化作用相对较弱。当纳米羟基磷灰石投加量为2%时，Pb浸出浓度削减率高达89.65%。淋洗/钝化联合修复大幅度降低了Pb和Cd的浸出浓度，降低了可还原态Cu残留量、可还原态和残渣态Cd残留量，以及弱酸提取态和可还原态Zn、Pb残留量。当EDTA和纳米羟基磷灰石投加量分别为1 g·L-1和1%时，土壤重金属总环境风险削减率达到74.12%。EDTA对土壤中Cu和Cd的洗脱效果较好，后续钝化修复作用有限，Pb和Zn则可通过淋洗/钝化联合修复大幅度提高削减环境风险削减率。

Joint remediation of heavy metal contaminated soil by EDTA and nano-hydroxyapatite

Soil leaching will cause the heavy metals activation, the leaching and deactivation combination could reduce this effect as it was used in the remediation of heavy metal contaminated soil. In this study, the effects of EDTA leaching, nano-hydroxyapatite deactivation and their combination in contaminated soil remediation on heavy metal elution rates, TCLP leaching concentration and chemical specification were studied. An environmental risk assessment method including residual concentration, bioavailability and physiological toxicity of heavy metals in soil was built to evaluate above remediation efficiencies. The results show that EDTA leaching treatments led to good elution rates for Pb and Cu, and high reduction rate for Zn leaching concentration. At 2 g·L-1 of EDTA dosage, the Zn leaching concentration decreased by 70.40%. Nano-hydroxyapatite treatments have a good deactivation effect on Pb and Zn, while a relatively weak deactivation effect on Cu and Cd. At 2% nano-hydroxyapatite additon, the reduction rate of Pb leaching concentration reached 89.65%. Their joint treatments significantly reduced the leaching concentrations of Pb and Cd, and the surplus of the reducible Cu, reducible and residual Cd in soil, weak acid extractable and reducible Zn and Pb. At joint addition of 1 g·L-1 EDTA and 1% nano-hydroxyapatite, the reduction rate of total environmental risk of heavy metals in soil reached 74.12%. Although EDTA treatment could achieve good elution effects of Cu and Cd, its subsequent deactivation was limited. The joint leaching and deactivation treatment could significantly reduce the environmental risks of Pb and Zn.